Folding of alpha(r)beta and epsilon beta reverse turns; A nanosecond molecular dynamics simulation of the hexapeptide MSALNT and the octapeptide NMSALNTL in water

Folding of the hexapeptide MSALNT and the octapeptide NMSALNTL were investi gated using 2.8 ns molecular dynamics (MD) simulations in aqueous solution. In the simulation, the central sequence SALN of the hexapeptide folded rap idly within 200 ps into an alpha(T)beta turn conformation ( type VIII confo rmation) and remained in this conformation for the rest of the trajectory. The sequence SALN of the octapeptide needed 2 ns to fold via epsilon beta c onformations into a similar conformation. The results join the sequences in to a growing group of sequences which have a tendency to form secondary str uctures and thereby to direct protein folding. The structures of the revers e turn conformations were in accordance with the experimental results (Haka lehto et al., Eur: J. Biochem. 250, 19-29 (1997)). The main driving force o f folding seems to be the hydrophobic interaction between the side chains o f Ala and Leu at the i+1 and i+2 positions of the beta-turn.